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Introduction to School. Tomas E. Gergely Summer School on Spectrum Management and Radio Astronomy Green Bank, June 2002. Spectrum Management.

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Radio Frequency Management Is Done by Experts Who Meld Years of Experience With a Curious Blend of Regulation, Electronics, Politics and Not a Little Bit of Larceny. They Justify Requirements, Horse-trade, Coerce, Bluff and Gamble With an Intuition That Cannot Be Taught Other Than by Long Experience

The National Radio Quiet Zone (NRQZ) wasestablished by the Federal Communications Commission (FCC) and by the Interdepartment Radio Advisory Committee (IRAC) in 1958 to minimize possible harmful interference to the National Radio Astronomy Observatory (NRAO) in Green Bank, WV and the radio receiving facilities for the United States Navy in Sugar Grove, WV. The NRQZ encloses a land area of approximately 13,000 square miles near the state border between Virginia and West Virginia.

The VLA consists of 27 antennas arranged in a huge Y up to 36km (22 miles) across -- roughly one and a half times the size of Washington, DC.Pattern. Each antenna is 25 meters (81 feet) in diameter; their output is combined electronically to give the resolution of an antenna 36km (22 miles) across, with the sensitivity of a dish 130 meters (422 feet) in diameter.

The resolution of the VLA is set by the size of the array -- up to 36km (22 miles) across. At the highest observing frequency (43GHz) this gives a resolution of 0.04 arcseconds:, sufficient to see a golf ball held by a friend 150km (100 miles) away. The dishes can move on a track and this allows the telescope to become the radio equivalent of a zoom lens.

The huge "dish" is 305 m (1000 feet) in diameter, 167 feet deep, and covers an area of about twenty acres. The surface is made of almost 40,000 perforated aluminum panels, each measuring about 3 feet by 6 feet, supported by a network of steel cables strung across the underlying karst sinkhole. It is a spherical (not parabolic) reflector.

Suspended 450 feet above the reflector is the 900 ton platform. Similar in design to a bridge, it hangs in midair on eighteen cables, strung from three reinforced concrete towers. The combined volume of reinforced concrete in all three towers is 9,100 cubic yards. Each tower is back-guyed to ground anchors with seven 3.25 inch diameter steel bridge cables. Another system of cables runs from each corner of the platform to large concrete blocks under the reflector. They are attached to giant jacks which allow adjustment of each corner with millimeter precision.